1. Field of Invention
This invention relates to a method to remove volatile organic carbons from gas streams.
2. Description of Prior Art
Industrial operations emit an enormous amount of hazardous air pollutants (HAPs) into the atmosphere each year. A large fraction of these HAPs are volatile organic carbons (VOCs) required for emission control by Clean Air Act Amendments of 1990 and state regulations. VOCs are also referred to as volatile organic compounds, volatile organic chemicals, or volatile oxidizable carbons. VOCs have gained prominence in air and water pollution control practice over the past decade as a result of heightened environmental and health concerns and the introduction of new regulations. VOCs are precursors of ground-level ozone, which contributes to smog formation. The overall chemistry is a complex interaction between VOCs, NOx and ozone which results in the formation of photochemical smog. Conventional technologies such as incineration and thermocatalytic oxidation are usually found to be expensive to implement and have a tendency to result in secondary pollution. Small emitters of VOCs such as dry cleaners, bakeries, restaurants and microbreweries are also coming under environmental scrutiny, especially in such environmentally sensitive areas as the South Coast Air Quality Management District in Southern California. Other sources of VOCs can include waste water treatment plants, light manufacturing and small businesses using solvents such as cabinet makers and musical instrument repair shops. Even an artist studio is a potential point source of VOCs due to the solvents used in paint, shellac, etc. The result is an urgent need to develop small and relatively inexpensive methods to eliminate VOCs from these point sources.
Different types of industrial operations and small businesses emit different types of VOCs. A bakery or brewery will emit ethanol. A dry cleaner will emit halogenated compounds such as terachloroethylene or clear petroleum distillate (Stoddard Solvent). Light manufacturing will emit solvent fumes such as methyl ethyl ketone (MEK) or toluene. Even a seemingly environmentally benign business as a greenhouse can emit a significant amount of terpenes, which can function as a greenhouse gas. Paint spray booths and adhesive tape manufacturers can emit significant amounts of aromatic solvents. A robust method to eliminate VOCs will also have military uses such as being mounted on the air inlet vents of a naval vessel to destroy nerve gas or biological agents during an attack.